The present invention relates to an apparatus and method for rendering an antialiased image, which are suitable for use in an entertainment system, such as a game machine, and a computer system.
Nowadays, the advent of highly-integrated, high-speed processors and memories has enabled real-time generation of three-dimensional images, which has hitherto been difficult to achieve. Thus, for example, a video-game machine is enabled to display three-dimensional images with realism.
When a three-dimensional image is displayed, the three-dimensional image is resolved into a plurality of polygons (that is, unit figures). Then, the entire three-dimensional image is rendered by rendering each of these polygons.
Practically, the displaying of this three-dimensional image is performed by performing geometry processing, such as coordinate transformation, clipping processing and lighting processing, on data representing the polygons which constitute the three-dimensional image, and then performing perspective projection conversion processing on resultant data obtained by such geometry processing to thereby convert three-dimension space data into data representing pixels arranged on a two-dimensional plane.
When such a three-dimensional image is rendered, the position of each of the polygons, which is represented by a floating or fixed point number, is converted into an integer number so as to be made to correspond to a pixel located at a fixed position on the screen of a display apparatus. Thus, aliasing occurs. Further, stair-step-like distortions called “jaggies” of a display image are caused owing to this aliasing. An occurrence of such aliasing or a jaggy may give a sense of incongruity to a user watching the three-dimensional image. Especially, in the case that this three-dimensional image is a dynamic image, flicker may be caused in this image.
Thus, a conventional image rendering apparatus reduces jaggies by virtually dividing each pixel into finer units called “sub-pixels” and then calculating the intensity of light of each of the sub-pixels according to a ray tracing method and thereafter averaging the calculated intensities of light of the sub-pixels of each pixel.
Further, another conventional image rendering apparatus reduces the jaggies by first generating a high-resolution image and then performing filtering on the image thereby to decrease the number of pixels and to antialias the image.
However, generally, a dynamic image comprises 20 to 30 frames or so per second. Thus, the rendering of a dynamic image needs to perform the calculation of the intensity of light of each of the sub-pixels according to the ray tracing method 20 to 30 times per second. Therefore, the former conventional image rendering apparatus, has drawbacks in that such calculations take time and that a dynamic image cannot be antialiased in real time.
Furthermore, the latter conventional image rendering apparatus, which is adapted to antialias (that is, reduce jaggies) by first generating a high-resolution image and then performing filtering on the image thereby to decrease the number of pixels, has drawbacks in that a buffer memory and a Z-buffer, each of which has large capacity and operates at a high speed, are needed when a dynamic image is displayed, and, thus, increasing the manufacturing cost and size of the apparatus increase.